Induction Drugs - Etomidate Exam 2 Flashcards
What is the mechanism of action of etomidate?
binds to GABA-A receptors
open Cl-channels
cell hyperpolarization
What is unique about Etomidate’s organic chemical structure?
It is the only carboxylated imidazole containing compound.
What is the induction dose for etomidate?
0.3 mg/kg IV
What is the onset and peak of etomidate?
- Onset: 1 min
- peak: 2 mins
what is the half-time of etomidate?
2-5 hours
At what pH is etomidate water-soluble vs lipid-soluble?
- weak base drug
- water soluble = acidic pH
- Lipid-soluble = physiologic pH
What percentage of etomidate is propylene glycol? What is the result of this?
35% propylene glycol = pain on injection
What is an alternative route for etomidate administration? Benefits of this?
- Sub-lingual etomidate
- bypass hepatic metabolism
Why does etomidate have a low incidence of myoclonus?
Trick Question. Etomidate has a high incidence of myoclonus, just like all other induction agents.
How much of it is protein bound? What protein does it bind to?
- 76% albumin
What is etomidate’s Vd? How does clearance compare to thiopental? What is the result of this clearance?
Large Vd
5x faster > thiopental = prompt awakening.
What metabolizes etomidate? What is the elimination profile?
- CYP450
- plasma esterases
- 85% via urine, 10-13% via bile
- no cummulative drug effect/no hangover
What is the best use for etomidate?
- Induction for unstable cardiac patients. (Minimal changes to HR, SV, CO, contractility)
- Good choice for low EF
- alternative to propofol or barbiturates for induction
What needs to be used concurrently with etomidate when performing a laryngoscopy? Why?
Opioids
etomidate has no analgesic effects.
What is Etomidate’s most common side effect? How often does this occur?
- Involuntary Myoclonic Movements
- (50 - 80 %) of administration
List in order the probability of myoclonus side effect: etomidate, thipoental, propofol, and methohexital.
- Etomidate 50-80%
- Thipoental 17%
- Methohexital 13%
- Propofol 6%
What can be administered with etomidate to prevent myoclonus?
- Fentanyl 1-2 μg/kg IV
- benzodiazepines
- (use caution in patients with seizure history)
Etomidate has a dose dependent inhibition of the conversion of cholesterol to _________. What does this mean clinically?
- Cortisol
- adenocortical suppression = inhibits natural stress response
- severe hypotension, longer on vent
How long does adrenocortical suppression with etomidate last?
What two pathologies would cause you to hesitate before giving etomidate?
4 - 8 hours.
Sepsis & hemorrhage (anything where you need an intact cortisol response).
how does thiopental and etomidate compare in cortisol regulation?
- Etomidate = decrease in plasma cortisol
- thiopental = no decrease in plasma cortisol
What are etomidate’s effects on CBF & CMRO₂?
↓CBF & ↓CMRO₂ 35-45%
What effect does etomidate have on cerebral vessels and ICP?
- Direct cerebral vasoconstrictor
- ↓ICP
CMRO₂ is coupled with both CBF and _______.
CMRG (cerebral metabolic requirement of glucose)
What is the EEG profile of etomidate?
- More excitatory than thiopental
- May activate seizure foci
- may increase amplitude of SSEP
What is SSEP?
- Somatosensory Evoked potential (SSEP)
- measures the time and amplitude of electrical signals from nerve to brain
Though etomidate is great for cardiac patients, what condition can result in significant hypotension if not treated prior to induction?
- Hypovolemia
- decrease in SVR with >0.45 mg/kg IV
What CV changes are expected with low doses?
- minimal changes
- decreased PAP
Does etomidate cause histamine release?
Trick question. Etomidate does not release histamine.
What is the pulmonary profile of etomidate?
- Less respiratory depression than barbiturates
- Rapid IV produces apnea
- Stimulates CO₂ medullary centers (respiratory drive)
How is respiratory drive affected with etomidate?
- VT decreases are offset by transient increase in RR (3-5mins)
- CO2 medullary stimulation
